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48k Speccy chucks a wobblerI've got a problem with my rubber keyed 48k speccy. When it is first switched on everything is fine but after a couple of minutes the picture on scr…
... as if the contents of lower memory are becoming corrupted. Once ... /> The problem could be the lower RAM ICs themselves, though usually faults ... switching transistors and consequently the lower RAM too. If this Spectrum still ... -
Difficult to find upper RAM fault.I've recently repaired an issue 3B 48K Spectrum that had a tricky to diagnose upper RAM fault, so I thought I'd post a report of what I found here. …
... never tries to test upper RAM, so I can boot ... this ROM doesn't use lower memory at all (except ... can boot a Spectrum with lower RAM bad chips. System variables, ... all located into non contended RAM.
Depending ... the damage in low RAM, I can even see ... -
TR4 is goneMy TR4 transistor is burned. Can I replace this transistor with a TIP31B or C ? My 4116 RAM ic?s are showing +0.05V, +5V and +8.49V... :) My Spectru…
[QUOTE=guesser;617666]Huh? How is that possible if the -5v supply to lower ram is missing? :-o[/QUOTE]
I don't know. :)
All keys work fine.
But when I hit ENTER, the Speccy resets. -
Help with iplayer 'watch again' type thingDon't really know how this works but is there any way I can watch match of the day? It just finished and I want to see the man u highlights I've got…
Hmm still not seeing it. might be a region thing, I can only see MOTD 'Wales' from the 3rd. thanks though, got the main info sorted -
What if there was no memory or space limitation?What if there was no memory or space limitation? We've had topics about the limitations of the Speccy's hardware, topics where we discussed how good …
... different syntax to address the RAM disc, and obviously machines ...
Alas BASin does not support +3 RAM disk syntax. ;)
Data - not sure yet ... ). Actually accessing the RAM disk does not seem to affect FRAMES ... -
What if there was no memory or space limitation?What if there was no memory or space limitation? We've had topics about the limitations of the Speccy's hardware, topics where we discussed how good …
[QUOTE=Paddy Coleman;626343]Alas BASin does not support +3 RAM disk syntax.[/QUOTE]
Not even if you force it using something like BAS2TAP? -
Zx 48k after the ic7805 other problemHi everyone, i am Tiago from Portugal, and i am trying to repair a Zx Spectrum 48K. the machine didn't do anything, no image, no sound, nothing. The…
... ) are all present at the lower RAM ICs (the 8 in a ... row on the lower left). I put the 4116 ... -
Zx 48k after the ic7805 other problemHi everyone, i am Tiago from Portugal, and i am trying to repair a Zx Spectrum 48K. the machine didn't do anything, no image, no sound, nothing. The…
... what appears if all the lower RAM ICs are removed.
lower RAM arrangement. -
Dark Screen, non working 48k Spectrum (rubber key)I have an issue 1 (I think) "dead cockroach" 48k Spectrum. On power up I get a dark screen and the machine is unusable - see pics. Any ideas on the…
... happens when there is a lower RAM fault. Are all the supply ... -
Wanted: Working 48K MotherboardMy Issue 3 48K motherboard is kaput, so I'm after a replacement. I've already fitted the case with a new membrane, so I don't need a whole new system…
... faults. I've desoldered the lower RAM ICs so far (no mean ... -
48k+ CPU SocketThink I've bitten off more than I can chew... After the desoldering my z80 went without incident, no damaged pads, tracks etc. I expected the socket…
... Blow
2. 4116's (lower ram) go bad
2. After ... />
Check your voltages on lower memory. -
Wanted: Working 48K MotherboardMy Issue 3 48K motherboard is kaput, so I'm after a replacement. I've already fitted the case with a new membrane, so I don't need a whole new system…
... faults. I've desoldered the lower RAM ICs so far (no mean ... -
4116 replaced by 4164 - "Noisy" paper?After I replaced my 4116's with 4164's and hooked them up to +5V, disconnected -5V and +12V, I have what looks like vertical lines in the paper, like…
... Z80 CPU (which has much lower output impedance than the old ... to be able to read lower RAM at the same time that ... the CPU was using upper RAM - because using resistors was way ... will cause CPU writes to lower memory and the ULA fail ... -
Using an ATX power supply - Spectrum 48kOK... I have an Issue 3 48K model and the DC-DC converter does not work and I can?t make it work. :( There is a MOD to use an ATX power supply on the…
... -DC circuit goes, often the lower ram gets fried too. Which is ... -
48k+ CPU SocketThink I've bitten off more than I can chew... After the desoldering my z80 went without incident, no damaged pads, tracks etc. I expected the socket…
You have checked that you have -5V +12V and +5V on the lower ram (4116's) and +5V on the high ram?
CHeck the spectrum repair guide on this site, is very useful. -
Issue 4S Schematics and DC-DC circuitA while ago I bought a Spectrum 4S that had problems tuning. I removed the RF tuner as I was not going to use it and did the composite mod. It worked…
... do with noisy voltage to lower ram. Need to investigate this when ... -
Spectrum 48K help neededI hav got an old Specrtum 48K issue 3. When I plug-in power connector it doesn't show the home screen (c) Sinclair.... From about 50 times trying to …
I have no ROM analyser or logic analayser.
I have tried many times but it would't initilase. Is there ar way tho check lower RAM chips or to disconnect upper RAM.
Is there are way to bring it working or can I throw it away. -
Spectrum 48K help neededI hav got an old Specrtum 48K issue 3. When I plug-in power connector it doesn't show the home screen (c) Sinclair.... From about 50 times trying to …
... ar way tho check lower RAM chips or to disconnect ... upper RAM.[/QUOTE]
The upper RAM chips are ... are often due to failed lower RAM, but it's a ... on screen.
Lower RAM checking is a matter of ... add-on test card with RAM test & LEDs ... -
Spectrum 48K help neededI hav got an old Specrtum 48K issue 3. When I plug-in power connector it doesn't show the home screen (c) Sinclair.... From about 50 times trying to …
[QUOTE=RetroTechie;636321]Lower RAM checking is a matter of ... add-on test card with RAM test & LEDs to indicate ... a logic analyser. If the RAM is detected as bad by ... -
48k+ CPU SocketThink I've bitten off more than I can chew... After the desoldering my z80 went without incident, no damaged pads, tracks etc. I expected the socket…
... (74LS154s) etc.
If lower ram has been connected all this ... one or more of the ram chips of lower ram is dead. -
Issue 2 Failed 48k to 128k upgradeI have been trying to upgrade my Issue 2 with the help of Velesoft, using this schematic; [IMG]http://i764.photobucket.com/albums/xx284/arioch1973/4…
... Issue 2 16k machine (replace lower ram with 4164s asap since I ... -
16k Issue 2 board and DivIDE load errorsI today got an Issue 2 16k board (thank you PMSR) that i added the logic and ram on to get a 48k machine. However, I am unable to load software from …
... socketed 4164s in place for lower ram. I can take a photo ... -
16k Issue 2 board and DivIDE load errorsI today got an Issue 2 16k board (thank you PMSR) that i added the logic and ram on to get a 48k machine. However, I am unable to load software from …
... , put 4164's as low ram (cutting -5V and +12V track ... +12V used to connect on lower ram). Put logic chips and 4164s ... as high ram. Add a buffer transistor to ... -
Successfully updated Issue 2 48k to 128k?Thanks to the donation by PMSR and through the very patient teachings of Velesoft, I have updated the Issue 2 to work with 128k. However. I have yet …
Z80 snapshot formatI read documentation for Z80 snapshot on WOS and see in table possibility insert ROM image to Z80 file. Here is full table: [code]The pages are numb…
... snapshot and load all existing ram pages. For example is possible ... v2/v3 with only 16kB ram (snapshot of ZX16). 128kB Z80 ... contain less than all 8 ram pages.
And reality ... . Missing ram pages in Z80 snapshot are ignored (not rewrite this ram page ...Replacing ZTX650 with BD139Today I blew up one of the GALs on one of my DivIDEs while testing on my Toastrack. Shorted M1 with 12V and the 12V circuit broke. I had to replace T…
... the 4116 memory modules for lower ram. Which is why I now ...Montana JonesJust recently discovered this game, looks quite good, quite basic gameplay but on screen 1 i just cant get the two items in the top right hand corner…
oddly enough... there's no M.J.1 in the series? (not seeing it in the archives)
or is that just another game that uses funny marketing techniques to make it interesting and famous product by adding "II" as for the succesful game follower... ?Coding for 128kHi all, I wonder if anyone can suggest any useful reading/threads/examples on the fundamentals of 128k coding. Chapter 24 of the +2 manual has prov…
... , 128 and +2 does not allow all RAM mode.
see ... /> [/QUOTE]
Yes, but im not sure if you recognize, that ... should know?
[/QUOTE]
Not much, that link above describes ... generate screen so contention does not occur
-if possible ( ...Semi-Dead Spectrum - Help RequestedI have finally got my hands on my two old Spectrums - neither of which work, but ideally I hope to get both of them working again. Spectrum number o…
Definitely replace all the electrolytic capacitors. A fault in some of them could destroy the lower RAM 4116 ICs and that'd probably be worse than the problem you've got now.
